The present invention relates to a laminated plate well adapted for use, for example, wind shield of a vehicle, which comprises a transparent glass layer located in outer side and a transparent resin layer located at the inner side of the glass layer in a laminated fashion.
There have been conventionally proposed laminated plates designed to include glass layers for the purpose of enhancing weight reduction and providing reinforcement. One of such known laminated plates includes a glass sheet laminated to the front face of a pre-molded or extruded resin sheet. Another composite body includes two glass sheets which are respectively laminated to both of the front and rear surfaces of a resin sheet so as to sandwich the resin sheet.
Such composite bodies have, however, the disadvantage that as the glass sheet is bonded to the pre-molded or extruded resin sheet, a gap would be created between the resin sheet and the glass sheet resulting in bonding defects if the surface of the resin sheet is not flat because of warp and shrinkage.
In addition, the pre-molded or extruded resin sheet should be treated with the greatest possible care not to hurt its surface, prior to bonding the glass sheet to the resin sheet.
The invention has been made to overcome the above problems and the prime object of the invention is therefore to provide a laminated plate and its producing method, the composite body comprising at least one glass layer that is located in front in order to reinforce the surface of the composite body, whereas the composite body is free from bonding defects and able to be easily produced without taking great care not to hurt the surface of the resin sheet.
The second object of the invention is to provide a laminated plate and its producing method, the composite body being strengthened in its bonding quality between the glass layer and the resin layer.
The third object of the invention is to provide a composite body and its producing method, the composite body being transparent and unnoticeable in respect of optical distortion or stress birefrin-gence.
The first object can be accomplished by a laminated plate according to the invention, comprising:
(a) a glass layer located in front and formed from a glass sheet; and
(b) a resin layer located at the back of the glass layer and molded by applying a low pressure by die clamping to a molten resinous material so as to be spread over the glass layer,
the glass layer and the resin layer being arranged in a laminated fashion. Alternative laminated plate may comprise:
(a) a first glass layer located in front and formed from a glass sheet;
(b) a second glass layer located behind and in parallel with the first glass layer and formed from a glass sheet; and
(c) a resin layer molded by applying a low pressure by die clamping to a molten resinous material placed between the first and second glass layers so as to be spread over these glass layers,
the first glass layer, the resin layer and the second glass layer being arranged in this order in a laminated fashion.
According to the invention, since the resin layer is molded by applying a low pressure by die clamping to the molten resinous material (in other words, by applying a low pressure to the overall molten resinous material) so as to be spread over the glass layer formed from a glass sheet, the bonding defects do not occur between the glass layer and the resin layer although the composite body is provided with the glass layer at least at the front face thereof for the purpose of providing reinforcement to the surface of the composite body. In addition, there is no need to treat the composite body with the greatest care not to hurt the surface of the resin sheet unlike the prior art.
The second object can be achieved by a laminated plate according to the invention, wherein xe2x80x9csurface irregularities treatmentxe2x80x9d is applied to make the joint surface of the glass sheet of the glass layer rugged, the joint surface joining to the resin layer, and wherein an intermediate layer is formed between the joint surfaces of the glass layer and the resin layer, the intermediate layer being formed from, for example, a thermoplastic elastomer which is adhesive to the glass sheet and to the molding and molten elastomer can relax the thermal stress caused by difference of heat expansion between the glass sheet and the molding, molten resinous material during molding of the resin layer.
In this way, the bonding strength between the glass layer and the resin layer is enhanced. The intermediate layer may be formed by primer coating in which the above elastomer is applied to the joint surface of the glass sheet joining to the resin layer or alternatively formed by affixing a resin film formed from the above resin material to the joint surface.
The third object can be accomplished by a laminated plate according to the invention, wherein the glass sheet is transparent and the molten resinous material is selected from the group consisting of polycarbonate, acrylic resin, polystyrene, amorphous polyolefin, and polyethylene terephthalate, and wherein the above low pressure is not more than 150 Kg/cm2.
In the composite body including the intermediate layer, the thermoplastic resinous material from which the intermediate layer is made may be selected from the group consisting of ethylene-vinyl acetate copolymer, thermoplastic polyurethane, ethylene-acrylate-maleic anhydride ternary copolymer, hydrogenated SBR (SBR hydride) and polyvinyl butyral, these materials exerting transparency after molding of the resin layer.
It should be noted that the thinner the glass sheet, the lighter the weight of the laminated plate.
To achieve the first object, a method for producing a laminated plate according to the invention is characterized in that: a glass sheet is first provided so as to come in close contact with the inner side of at least either one of dies for use in a compression molding machine and a molten resinous material to be supplied to a mold cavity being spread at a low pressure over the glass sheet, then the compression molding is carried out by clamping both dies to apply a low pressure to a molten resinous material to be supplied to a mold cavity such that the molten resinous material is spread over the glass sheet, whereby the laminated plate comprising, in a laminated fashion, a glass layer composed of the glass sheet and a resin layer molded from the molten resinous material that is spread by applying a low pressure thereto by die clamping can be formed.
To achieve the second object, the producing method may include primer coating in which a resinous material is applied before-hand to the joint surface of the glass sheet or pre-affixing of a resin film formed from the resinous material to the joint surface, the joint surface being joined to the resin layer to be molded from the molten resinous material, the resinous material being adhesive to the glass sheet and to the molding, molten resinous material and having the function of relaxing the thermal stress caused by differences of heat expansion between the glass sheet and the molten resinous material during the molding of the resin layer from the molten resinous material.
In order to provide transparency to the resultant, laminated plate and make its distortion unnoticeable or stress birefringence, the glass sheet should be transparent and the molten resinous material should be selected from the group consisting of polycarbonate, acrylic resin, polystyrene, amorphous polyolefin and polyethylene terephthalate, and the above low pressure should be no more than 150 Kg/cm2. The resinous material used in primer coating or constituting the resin film is selected from the group of thermoplastic resinous materials consisting of ethylene-vinyl acetate copolymer, thermoplastic polyurethane, ethylene-acrylate-maleic anhydride ternary copolymer, hydrogenated SBR (SBR hydride) and polyvinyl butyral. These materials exert transparency after molding of the resin layer.
Other objects of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.